Electrical Pulse-Driven Periodic Self-Repair of Cu-Ni Tandem Catalyst for Efficient Ammonia Synthesis from Nitrate

Electrocatalytic nitrate reduction sustainably produces ammonia and alleviates water pollution, yet is still challenging due to the kinetic mismatch and hydrogen evolution competition. Cu/Cu₂ O heterojunction is proven effective to break the rate-determining NO₃ ^- -to-NO₂ ^- step for efficient NH₃ conversion, while it is unstable due to electrochemical reconstruction. Here we report a programmable pulsed electrolysis strategy to achieve reliable Cu/Cu₂ O structure, where Cu is oxidized to CuO during oxidation pulse, then regenerating Cu/Cu₂ O upon reduction. Alloying with Ni further modulates hydrogen adsorption, which transfers from Ni/Ni(OH)₂ to N-containing intermediates on Cu/Cu₂ O, promoting NH₃ formation with a high NO₃ ^- -to-NH₃ Faraday efficiency (88.0±1.6 %, pH 12) and NH₃ yield rate (583.6±2.4 μmol cm^-2 h^-1 ) under optimal pulsed conditions. This work provides new insights to in situ electrochemically regulate catalysts for NO₃ ^- -to-NH₃ conversion.